The evolution of wireless communication to fifth generation (5G) standards and technologies provides higher data rates and greater capacity, with improved reliability and lower latency, which enhances mobile broadband services. 5G technologies also provide new classes of services for vehicular, fixed wireless broadband, and the Internet of Things (IoT).
A unified air interface, which utilizes licensed, unlicensed, and shared license radio spectrum, in multiple frequency bands, is one aspect of enabling the capabilities of 5G systems. The 5G air interface utilizes radio spectrum in bands below 1 GHz (sub-gigahertz), below 6 GHz (sub-6 GHz), and above 6 GHz. Radio spectrum above 6 GHz includes millimeter wave (mmWave) frequency bands that provide wide channel bandwidths to support higher data rates for wireless broadband.
To increase the capacity of 5G radio networks, Multiple Input Multiple Output (MIMO) antenna systems are used to beamform signals transmitted between base stations and user terminals. In 5G networks, a large number of MIMO antennas (e.g., hundreds of antennas) are employed for beamforming signals, which is often referred to as Massive MIMO, to provide beamformed transmission and reception that is focused on small areas of space around individual user terminals. Massive MIMO beamforming improves network throughput, energy efficiency, and interference rejection. Massive MIMO systems use a channel estimate of the radio frequency (RF) channel characteristics between the base station and the user terminal to determine beamforming coefficients for transmission and reception.
The specification of the features in the 5G air interface for user equipment (UE) is defined as 5G New Radio (5G NR). The combination of supporting multiple frequency bands, wider channel bandwidths, higher data rates, and Massive MIMO increases the number of uplink and downlink processing chains, power amplifiers, and RF front end components required in the UE. For user equipment such as a smartphone, the support of 5G NR features for both uplink and downlink communication increases power consumption that reduces the battery life of the smartphone, increases the complexity of managing in-device coexistence problems related to interference during simultaneous operation of Long Term Evolution (LTE) and 5G transmitters, and requires additional components that occupy more space in the constrained mechanical package of the smartphone, as well as increasing the cost of the smartphone.